The present invention is directed to a phase-shifter apparatus and method for construction and more specifically to a solid-state microwave digital diode phase shifter for noise and deception jamming and frequency translation (utilizing the serrodyne principle), for electronic antenna steering and electronic phaseshift applications.
One of the applications of the present invention is related to co-pending patent application Ser. No. 534,566, filed Sept. 22, 1983, the names of Asad M. Madni and Joseph Fala (Asad M. Madni is one of the co-inventors of the present application), entitled VELOCITY DECEPTION APPARATUS. The disclosure of the Madni/Fala application is hereby incorporated by reference.
That application discloses an electronic counter-measures (ECM) technique which produces slowly changing false doppler frequencies by a so-called velocity gate stealer (VGS). Such apparatus is mounted in an aircraft and when it receives a radar pulse from ground which is operating on the doppler system it pulls the velocity tracker of the ground radar off the target to drop it. The ground radar may then lock on the clutter or be forced into a reacquisition sequence. The above application as its phase shift apparatus uses a serrodynable digital phase shifter of the Schiffman type where each cell of the phase shifter is driven by an output of a multi-bit counter whose clock input in turn is driven by a voltage-to-frequency converter which has a pulse train output which responds substantially instantaneously to the analog value of a linear or second order function which produces the desired frequency translation. Thus, this performs as a velocity gate stealer which produces slowly changing false doppler frequencies.
As discussed in the above co-pending application, since the frequency change must occur in discrete steps, spurious frequencies are inherently generated. If these are minimized at several decibels below the main output frequencies, the spurious sideband signals are not deleterious to the overall system operation.
Additionally, there are several other applications of the present invention, such as: one of the several electronic steering elements for electronically steered antennas, frequency translation and electronic phase shift. The use of digital phase shifters for electronically steered radar is generally discussed in the February 1985 of Scientific American.